The specific aim of the proposed research is to design, prepare and test ligands for selective complexation of Li+ and K+ in the presence of Na+, Mg2+, and Ca2+. Fluorophores attached to the ligands will allow measurement of Li+ and K+ concentrations in blood plasma by chelation enhanced fluorescence. selectivity achieved for Li+ and K+ will be in the presence of Na+ concentrations typical of blood plasma, i.e., 135- 148 mmol.L-1. The Li+ ligand will be designed for use as a sensor to monitor Li+ levels in manic depressive patients being treated with Li salts. Therapeutic blood levels of Li+ are approximately 0.9-1.4 mmol.l- 1, so that the sensor ligand should display Li+ over Na+ selectivity of the order of 2000:1 to avoid interference from Na+. Rapid rises in K+ concentrations in patients undergoing surgery are a sign of the patient going into shock, so that real time monitoring of these levels is important. Blood K+ levels are about 4.5 mmol.L-1, making the targeted selectivity for K+ over Na+ about 1000:1. A long-term objective of the project is the attachment of successful ligands to optical fibers to produce probes that can simultaneously indicated pH, blood electrolyte, and blood gas levels. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE